Implant alignment

ABSTRACT

An apparatus for alignment of dental implants in which an implant in provided with a generally axial bore and a plurality of angled templates, each adapted for operative inter-connection with the bore of the implant. Each template includes a locator lug adapted for inter-engagement with the axial bore of the implant, each lug having a circular cross-section.

The present invention relates to the alignment of dental implants and toa method for their alignment. In the Probe, September 1998, 1 havedescribed a dental implant and a method for its insertion. In thisarrangement a site is selected so that it is in the middle of a ridge.The jaw bone is drilled using internally irrigated titanium alloy bursso that it is sited between the labial and palatal cortical plates,making sure that the adjacent teeth and anatomical structures areavoided. The implant is inserted until level with the bone.

Abutment or template selection is effected by using a trial abutment(template) which measures the restorative angle, allows the implant tobe positioned to the correct depth, and aligns the driving flat (or hex)in the correct plane

The trial abutment (template) should fit within the hollow prostheticenvelope. This ensures that the final abutment will be in the rightposition. Any adjustments to the position of the implant can now be madebefore it is integrated. The cover screw is then replaced, the wound issutured and the implant is allowed to integrate over a period of aboutsix months.

The depth to which the implants are placed is important since if theyare too deep this may result in bone loss (to the 1^(st) thread) whichis not ideal, and if they are not deep enough they may become exposedprematurely. That a trial abutment or template is necessary is shown bythe fact that otherwise there is no way that the angle of the abutmentcan be selected and the plane of orientation measured or changed unlessthis is done at the 1^(st) stage of surgery.

In order to achieve this, previously each template was provided with adownwardly depending lug provided with a plurality of driving planes forco-operation with similarly shaped receptor planes in the correspondingbore in which it was adapted to fit. Said “internal hex” arrangementscan be satisfactory but give rise to a number of problems. In the firstplace the internal driving planes have to be small and therefore theirmanufacture is relatively difficult. However because they can besubjected to significant rotational forces during positioning themanufacturing tolerances must be of a low order. Most of all theutilisation of the internal driving flats, as previously suggestedraises the difficulty that the dentist cannot be sure that the templateis fully “home” on the implant, which can give rise to misalignmentsonce full implant integration has occurred.

The need therefore exists for a template which will drive the implantduring rotation only if the template and the implant are fully engaged.Further there is a need to ensure that the turning moment applied by thetemplate to the implant is as positive as possible.

According to the present invention there is provided an apparatus forthe alignment of a dental implant, said apparatus comprising an implantcomprising a generally axial blind bore and a plurality of angledtemplates each adapted for operative inter-engagement with the bore ofthe implant; characterised in that each template comprises a locator lugfor inter-engagement with the axial bore of the implant, said lugcomprising a circular cross-section. It is preferred that the lug shallhave a frusto-conical section for inter- engagement with a correspondingbore in the implant (or taper-lock). In a further embodiment thefrustro-conical section includes a plurality, preferably four, ofdriving planes for co-operation with the bore of the implant. It is alsopreferred that the frusto-conical section terminates towards its freeend in a portion of a smaller diameter.

Alternatively the locator lug may be of a right cylindricalconfiguration and a plurality of driving planes are provided internallyof the body of the template for operative interconnection with acorresponding set of driving flats positioned about the mouth of thebore of the implant.

In an alternative arrangement the locator lug is separate from thetemplate and the template is formed with a bore that is adapted to beco-axial in use with that of the implant.

In a preferred embodiment the template terminates at its intended upperend remote from the lug in a shaft or peg which has a generally elongateconfiguration, often of a right cylindrical shape, so that whatever itsrotational position it will mimic the correct angle of the existingteeth in use.

By means of the present invention the implant will only rotate to itsfinal position when fully inter-engaged. Partial inter-engagement, andhence misalignment of the template with the implant, is thus much lesslikely to occur.

The invention will now be described, by way of illustration only, withreference to the accompanying drawings wherein:—

FIG. 1 shows a side view from below of a first template of theinvention;

FIG. 2 shows a side view from below of a final abutment for use with theinvention;

FIG. 3 shows a side view of the first template in cross-section;

FIG. 4 shows a side view from below of another template of theinvention;

FIG. 5 shows a side view a template somewhat as shown in FIG. 1 but witha plurality of driving planes disposed in frusto-conical portion.

FIG. 6 shows an exploded side view of an abutment with a frusto-conicallug in part vertical section;

FIG. 7 shows a side view in part section of a template with lockingflats to form a external “hex” on the implant;

FIG. 8 shows an exploded side view in part section of an abutment andimplant in accordance with FIG. 2,

FIG. 9 shows a side view part section of the arrangement of FIG. 4, and

Turning first to FIGS. 1 to 4, FIG. 1 shows a template (comprising amain body which is generally angled to the axis of an implant.

A template alignment shaft 3 and body 4 are angled to the axis of theimplant in use by an amount varying from 5° and 45° degrees. Thetemplate and the implant are arranged such that they are correctlypositionable prior to integration relative to a bore positioned in thejaw by means of the correct orientation of the shaft 3 relative to theexisting teeth in use.

As is shown in FIG. 1, the body of the template 1 terminates ingenerally downwardly depending frusto-conical portion 5 and a rightcylindrical extension piece 6. It is arranged that frusto-conicalportion 5 and the extension piece 6 are generally co-axial with the boreof the implant 2. As will be appreciated the locking force between theimplant and the template is only established when they are fullyinter-engaged. A similar arrangement to that shown in FIG. 1 is shown incross-section in FIG. 3.

A similar arrangement is shown for an abutment 30 in FIG. 2. In thisarrangement the body 32 is provided along its length with an upper mostaperture 36, said aperture extending downwardly to terminate at a lowermost aperture 38. A frusto-cone 34 extends at an angle to the body 32,the aperture 36 terminating in the frusto-cone. A bolt (shown generallyin FIGS. 6, 7 and 8) passes through the body to locate the template onthe implant as necessary. It is desirable that such a bolt should beprovided with an Allen keyway for tightening purposes.

FIG. 4 provides an alignment shaft 3 similar to that shown in FIG. 1 anda body 4, again similar to that shown in FIG. 1 with the exception thatin this arrangement a rotation aperture 12 is provided through the body4 in order to locate a rotation rod therein. The arrangement of FIG. 4also provides a downwardly depending locator lug 11 which has a circularcross-section which is in the form of a right cylinder for location in acorresponding bore in the implant.

FIG. 5 shows an arrangement similar to FIG. 1 but wherein thefrusto-conical portion 5 includes a plurality of driving planes 20, butwherein the radially outer edge (21) of the planes 20 has afrusto-conical aspect so that it forms a continuous surface with thefrusto-conical portion 5. This allows the template 1 to inter-engagewith a co-operating axial bore while also having a positiveinter-engagement therewith.

An exploded diagram of the implant and abutment assembly according tothe present invention, somewhat as shown in FIG. 2, is shown in FIG. 6.In this arrangement, shown in partial cross-section, a threaded bolt 18is provided with an Allen key aperture 19 and is adapted for location inan upper bolt aperture 36. The shaft of the bolt 18 passes through thefrusto-conical portion of the abutment 30 and through the lower boltaperture 38.

With the implant and the template fully inter-engaged, the threaded endof the bolt 18 enters a recess 16 in the implant 2. Implant 2 isprovided to its exterior with a ribbed edged body 14 terminating towardsits upper edge in an annular implant head 13. At its other (lower) endis a cut out 15 for reasons of bone integration.

In use the bolt 18 secured in the aperture 36 passes into the recess 16and into the screw thread cavity 17, whereupon rotation of the Allen keyin aperture 19 causes the abutment 30 to lock onto the implant 2 in atemporary fashion. The Allen key can then be used to rotate the abutment30 into its correct orientation relative to other teeth. The bolt 18then may be withdrawn without disturbing the implant 2 and the abutment30 may be removed and recorded.

A similar arrangement is shown in FIG. 7 but in this instance bolt 18 isprovided with standard external driving flats 18′, while the template 1is provided with internal driving flats 10 only.

In FIG. 8 there is provided an exploded arrangement showing in partsection a further embodiment. Its modus operandi has been fullydescribed with regard to FIG. 6. The only difference lies in thatinstead of the frusto-conical portion 34, there is provided a pluralityof internal locking flats 40 for inter-engagement with an external “hex”20 secured about the mouth of the recess 16 in the implant 2. It will beappreciated that the effect of the external hex 20 is to locate the body32 of the abutment 30 but only when the bolt 18 is fully inter-engagedby means of the Allen key engaged in the aperture 19. Again by means ofthe Allen key (not shown) abutment 30 can be placed in its correctposition by thereby rotating the implant 2 and subsequently removing thesame.

A similar arrangement is shown in FIG. 9 which shows the arrangement ofFIG. 4 in side view and in partial cross-section. The locator lug 11 isright cylindrical and acts to locate the template 1 in position in theimplant 2 but of course only once fully inter-engaged. It may then berotated once the flats 10 have been inter-engaged with the external hex20 as shown in FIG. 8.

1. Apparatus for alignment of a dental prosthesis, said apparatuscomprising: an implant for insertion in the jaw bone of a patient, theimplant having a generally axial bore internally threaded over a portionof its length; an abutment to which the prosthesis will be formed, andwhich is locked to the implant by interaction of a separable bolt whichis externally threaded over a portion of its length with the internalthreads of the implant; and a plurality of angled templates for use withsaid implant, each of said templates being a single piece and comprisinga body having a right cylindrical, locator lug at one end thereof and aright cylindrical alignment shaft at an opposite end thereof, saidlocator lug being constructed and arranged to interact with the axialbore of the implant only when the implant and template are fullyinter-engaged, and said alignment shaft is constructed and arranged atan inclined angle to the locator lug for orientation of the alignmentshaft relative to teeth adjacent the implant, wherein each template ofsaid plurality of templates has a different inclined angle between 5 and45′, and one of said templates is selected to determine a correctabutment to use, the selection of said one template being made on thebasis of the orientation of the alignment shaft thereof relative to theteeth adjacent the implant.
 2. Apparatus according to claim 1, whereinthe locator lug comprises a frusto-cone having a portion of smallerdiameter towards a free end of the lug.
 3. Apparatus according to claim2, wherein the locator lug further comprises an extension pieceextending generally axially from the frusto-cone towards the free end ofthe locator lug.
 4. Apparatus according to claim 3, wherein thefrusto-cone comprises a plurality of driving flats disposed on portionsof its surface, constructed and arranged for inter-connection withcorresponding elements on the implant.
 5. Apparatus according to claim2, wherein the frusto-cone comprises a plurality of driving flatsdisposed on portions of its surface.
 6. Apparatus according to claim 1,wherein each said template comprises a shaft remote from the locatorlug, said shaft being adapted to mimic the adjacent teeth.
 7. A methodfor alignment of a dental prosthesis, said method comprising: insertingan implant in the jaw bone of a patient, the implant having a generallyaxial bore internally threaded over a portion of its length; providing aplurality of angled templates for use with said implant, each of saidtemplates comprising a body having a right cylindrical locator lug atone end thereof and a right cylindrical alignment shaft at an oppositeend thereof, said locator lug being constructed and arranged to interactwith the axial bore of the implant only when the implant and templateare fully inter-engaged, and said alignment shaft is constructed andarranged at an inclined angle to the locator lug for orientation of thealignment shaft relative to teeth adjacent the implant, wherein each ofsaid plurality of templates has a different inclined angle between 5° to45°; selecting one of said templates on the basis of a correctorientation of the alignment shaft thereof relative to the teethadjacent the implant; and selecting an abutment to which the prosthesiswill be formed based on the inclined angle of the selected template,said abutment being locked to the implant by interaction of a separablebolt which is externally threaded over a portion of its length with theinternal threads of the implant.